1. Field of the Invention
The present invention relates to a briquetted fertilizer which is suitable for forest fertilization.
2. Description of the Prior Art
In general, from the viewpoint of the growth of trees, fertilization is most important during the period of from 3 to 5 years after the transplantation of the seedling. In the transplantation itself, a compound fertilizer or a straight fertilizer, such as urea have generally been employed. However, these fertilizers become ineffective in about one year, even if they are of the type which is gradually efficacious. Therefore, it is necessary to apply a topdressing once a year during the first five years after the transplantation of the seedling. This process requires a significant amount of labor because it must be done on an individual, one by one, basis for each tree in a very wide area such as a tree-planting field. However, if a fertilizer can be obtained which is capable of maintaining its effect over a period of about 3 to 5 years while seedlings are being vigorously grown, the topdressing will not be needed. The fertilizer placed on the planting pit at the time of planting will suffice.
Unfortunately, no such fertilizer has yet been reported. Various means for maintaining the effect of a fertilizer over an extended period of time have been suggested: e.g., a method is known of obtaining a fertilizer granule of large diameter by compression molding a gradually efficacious fertilizer. However, the granulated fertilizer thus obtained is lacking in the capability for shape retention in water so that it is not effective as a maintenance fertilizer for trees. Moreover, it is very difficult to compression mold a fertilizer component by itself and the resulting molding yield is low. Thus, such a method is not practical. Consequently, it would be most desirable to have a fertilizer for trees which may be applied when seedlings are transplanted and which remains efficacious throughout long periods of vigorous seedling growth.